Early lignin pathway enzymes and routes to chlorogenic acid in switchgrass (Panicum virgatum L.)
- 1.4k Downloads
Studying lignin biosynthesis in Panicum virgatum (switchgrass) has provided a basis for generating plants with reduced lignin content and increased saccharification efficiency. Chlorogenic acid (CGA, caffeoyl quinate) is the major soluble phenolic compound in switchgrass, and the lignin and CGA biosynthetic pathways potentially share intermediates and enzymes. The enzyme hydroxycinnamoyl-CoA: quinate hydroxycinnamoyltransferase (HQT) is responsible for CGA biosynthesis in tobacco, tomato and globe artichoke, but there are no close orthologs of HQT in switchgrass or in other monocotyledonous plants with complete genome sequences. We examined available transcriptomic databases for genes encoding enzymes potentially involved in CGA biosynthesis in switchgrass. The protein products of two hydroxycinnamoyl-CoA shikimate/quinate hydroxycinnamoyltransferase (HCT) genes (PvHCT1a and PvHCT2a), closely related to lignin pathway HCTs from other species, were characterized biochemically and exhibited the expected HCT activity, preferring shikimic acid as acyl acceptor. We also characterized two switchgrass coumaroyl shikimate 3′-hydroxylase (C3′H) enzymes (PvC3′H1 and PvC3′H2); both of these cytochrome P450s had the capacity to hydroxylate 4-coumaroyl shikimate or 4-coumaroyl quinate to generate caffeoyl shikimate or CGA. Another switchgrass hydroxycinnamoyl transferase, PvHCT-Like1, is phylogenetically distant from HCTs or HQTs, but exhibits HQT activity, preferring quinic acid as acyl acceptor, and could therefore function in CGA biosynthesis. The biochemical features of the recombinant enzymes, the presence of the corresponding activities in plant protein extracts, and the expression patterns of the corresponding genes, suggest preferred routes to CGA in switchgrass.
KeywordsPhenylpropanoid pathway Lignin Flavonoids Chlorogenic acid
We thank Drs. Jerome Verdier and Lina Gallego-Giraldo for critical reading of the manuscript. This work was supported by the BioEnergy Science Center, a US Department of Energy Bioenergy Research Center supported by the Office of Biological and Environmental Research in the DOE Office of Science.
- Comino C, Lanteri S, Portis E, Acquadro A, Romani A, Hehn A, Larbat R, Bourgaud F (2007) Isolation and functional characterization of a cDNA coding a hydroxycinnamoyltransferase involved in phenylpropanoid biosynthesis in Cynara cardunculus L. BMC Plant Biol 7:14PubMedCentralPubMedCrossRefGoogle Scholar
- Fu C, Mielenz JR, Xiao X, Ge Y, Hamilton CY, Rodriguez M Jr, Chen F, Foston M, Ragauskas A, Bouton J, Dixon RA, Wang Z-Y (2011) Genetic manipulation of lignin reduces recalcitrance and improves ethanol production from switchgrass. Proc Natl Acad Sci USA 108:3803–3808Google Scholar
- Mahesh V, Million-Rousseau R, Ullmann P, Chabrillange N, Bustamante J, Mondolot L, Morant M, Noirot M, Hamon S, de Kochko A (2007) Functional characterization of two p-coumaroyl ester 3′-hydroxylase genes from coffee tree: evidence of a candidate for chlorogenic acid biosynthesis. Plant Mol Biol 64:145–159PubMedCrossRefGoogle Scholar
- Shen H, He X, Poovaiah CR, Wuddineh WA, Ma J, Mann DGJ, Wang H, Jackson L, Tang Y, Neal Stewart C Jr (2011) Functional characterization of the switchgrass (Panicum virgatum) R2R3-MYB transcription factor PvMYB4 for improvement of lignocellulosic feedstocks. New Phytol 193:121–136PubMedCrossRefGoogle Scholar
- Shen H, Mazarei M, Rudis MR, Tang YH, Hisano H, Jackson L, Li G, Hernandez T, Chen F, C. Stewart Jr N, Wang Z, Dixon RA (2013). A genomic approach to deciphering pathways for lignin biosynthesis in switchgrass (Panicum virgatum L.). Plant Cell, in revisionGoogle Scholar
- Stockigt J, Zenk MH (1975) Chemical syntheses and properties of hydroxycinnamoyl-Coenzyme A derivatives. Z Naturforsch [C] 30:352–358Google Scholar
- Vanholme R, Cesarino I, Rataj K, Xiao Y, Sundin L, Goeminne G, Kim H, Cross J, Morreel K, Araujo P, Welsh L, Haustraete J, McClellan C, Vanholme B, Ralph J, Simpson GG, Halpin C, Boerjan W (2013) Caffeoyl shikimate esterase (CSE) is an enzyme in the lignin biosynthetic pathway. Science 341:1103–1106PubMedCrossRefGoogle Scholar
- Zhang J-Y, Lee Y-C, Torres-Jerez I, Wang M, Yin Y, Chou W-C, He J, Shen H, Srivastava AC, Pennacchio C, Lindquist E, Grimwood J, Schmutz J, Xu Y, Sharma M, Sharma R, Bartley LE, Ronald PC, Saha MC, Dixon RA, Tang Y, Udvardi MK (2013) Development of an integrated transcript sequence database and a gene expression atlas for gene discovery and analysis in switchgrass (Panicum virgatum L.). Plant J 74:160–173PubMedCrossRefGoogle Scholar